Speech recognition apparatuses are well known in the art. A speech recognition apparatus can be used to activate a number of task including a telephone. However, the algorithm used in speech recognition is complex and has required the use of a dedicated signal processor. The use of a dedicated signal processor has increased the cost of the apparatus.
Although a first difference technique has been used in speaker recognition analysis (see "Telephone-Line Speaker Recognition Using Clipped Autocorrelation Analysis", by H. Ney, Proc. ICASSP81 (Atlantic, 1981) p. 188-192)), such an analysis has not been done in speech recognition heretofore.
The basic dynamic time warping (DTW) algorithm, used in speech pattern matching process, is well known in the art. It is disclosed in the article "Dynamic Programming Algorithm Optimization for Spoken Word Recognition" by Hiroaki Sakoe and Seibi Chiba, IEEE Trans. Acoust., Speech, and Signal Process, Vol. Assp-26, pp. 43-49, February, 1978. However, that algorithm does not provide a satisfactory solution to the window skewing problem.
A modified DTW algorithm is disclosed in "A Modification Over Sakoe and Chiba's Dynamic Time Warping Algorithm for Isolated Word Recognition", by K. Paliwa, A. Agarwal and S. S. Sinha, IEEE Int'l Conf. Qn Acoust. Speech and Sig. Proc., Vol. ICASSP-2, pp. 1259-61, May 1982. Although this algorithm attempts to solve the problem of window skewing, it is also subject to error.
It is also known in the prior art to "prune" a DTW operation. In a pruning operation, if a search of k words results in an ith word having the lowest value of X, then in the DTW operation on the subsequent words, if during the summation operation the difference of the coefficients at any point in time exceeds the best score, then the DTW operation is terminated. See "Performance Trade-Offs and Search Techniques for Isolated Word Search Recognition", by R. Bisiani, A. Waibel, IEEE Int'l Conf. On Acoust. Speech and Sig. Proc., Vol. ICASSP-1, pp. 570-73, May 1982. However, this technique still requires a considerable amount of computation.
Speech activated phones are also well known in the art. However, they have not provided a mechanism by which questionable choices of the particular speech pattern to a stored speech pattern can be resolved. Thus, they are prone to error and cannot be resolved by user input. These and other considerations have not permitted a speech activated telephone to use an inexpensive general processor wherein other novel features may be implemented, without a great deal of cost.
In the prior art a single line telephone is connected to a single pair of physical wires labeled tip and ring. Since communication must be effected in both directions through the tip and ring lines, a balance transformer has been used to isolate the tip and ring lines from the transmit and receive lines internal within the telephone. Such a balance transformer is expensive and is bulky.
Prior art telephones have provided for the monitoring of the telephone line to which it is attached. However, the typical monitoring functions have been limited to ringing, hold, and busy. The telephone apparatus has not been able to display the status of whether or not the telephone is connected at all to the line without placing the telephone off hook to determine if the telephone is connected to the line.